Method and apparatus for producing shock waves



Jan. 5, 1954 5,-sM1 2,664,850

METHOD AND APPARATUS FOR PRODUCING SHOCK WAVES Filed Nov. 26, 1949 I I FIXED SPEED OR I I l l g WITH SPEED CHANGE 3 /78 CONTROLS, 1 76 A w v souacs OF NR UNDER PRESSURE PEESSUR REGULATOR AND CONTRO ALVES mddmazi Patented Jan. 5, 1954 METHOD AND APPARATUS snocK WAY-E Franklin S. Smith, Han den, Conn. ApplicationNovemberZfi, 19;4 9,erial N0. 128,655

14 Claims. (-01. 15 -137) This invention relates to a method and apparatus for the generation of shock waves in air.

vOne of the objectsiof this'invention is to provide a practical and economical method and apparatus of theabove nature. Another object'is to provide an apparatus for generating shock waves that will be relatively'inexpensive in .con struction and operation; Another object is to provide an apparatus and method vfor generating shock waves ,in a manner that is relatively low in poweriinput orvpower consumption and hence iseconomical to operate. Another object is .to provide a method and apparatus of the above-mentioned nature capable of suitable variationior nexibilityof control .or operation so that a relatively' wide range of conditions, such as the generation of weak or of strong shock waves as may tbe desired, may be achievedaccording to the particular objective or Purpose of applica tion or use ofithe shock wave.

' Another obj ect, is toprovide. a method and apparatus for generating shock waves that will be les'szcostly in first cost of equipment required as well-as less costly in operation. ,Another object i'sYto facilitate the application ofshock waves to various useful purposes, such as the subjection to shockwaves of test specimens or shapes or structures, "or of test specimens 7 of various mas terials tor compositions of matten'particularly for thlstu'dy and investigation of the effects thereon of shock waves,]o r such asthe subjection-to shock waves ofvarious foodpioducts containingfinsect infestation in its various forms or stages to iacilitate the destruction of such insect .iife and also to ,facilit'ate'the study and investigation of the efiects thereon of shock waves, .orsuch as the subjection to shockwaves of vegetable products in kernel iorm, for example rice, to effect the loosening or removalthere fromlof thehull or shell-like structure encasing thekernel, as well asto studyandinvestigate the, effectsthereon of shock waves.

1 Another. object of this invention .is to provide an apparatus,,and a vmethod of operating and controlling thesam'e, for the generation of shock waves-and which apparatus can be embodied in iar mo'r compact, less costly, and more efficient vform than SLIChLheretQfQreQkn Wn n paratuslas the so-called wind tunnel, and thereby to vfacilitate and expedite study, research, and investigation of shock waves and their, effects. ,Another object is to provide a .shoo'k-wave-gigneratting ap- Daratus that isvrelaltively lowiin povwer lconsuniption and therefore capable of less expensive and relatively economical operation and thereby also stimulate and facili at u y and investi ation of shock waves andtheiractions and efiects;

Other objects will "be in partobviousor in part pointed outihereinaiter.

The invention accordingly consists in the fee.-

u es of const uct o mb a i of e ments, arrangements of parts, and in the several steps nd rel tion and order f a h or he am to one or more of the others, all will be illustraa ly desoribedaher in. and hes ope' o th fanplication of Wllifih will beindicated in the followin cla' m In the accompanying drawing in w i h is hown'by way of i lus rati lt n o th v io s possible embodiments .Ofthefl mechan calfee u es of mv n entionp Fi 1 is a front eleva on oi the appa a us. with one of the pa ts shown in ice alve ial s ction, certain other parts in .diag mma al y ndicated;

Fig, 2 is a top view or elevation as seen from above in Fi 1, certain pa ts be ng h n n. central horizont ls ctio and c rtain other P ts bein vhro'lgen away in orde to in cate ert other a t m re clearly. and

Fig. 3 is a detached Vflrticaltransfer sectional View 9 one o the part as seen a ong line 3-3 cities. ,1 and 2- Simila referenc c racter u te v to simila part 'tihroush utithe seve al views o idrav "Referring to Figs. 1 and ",I provide a rotor L 'illustrativelyoiaconst uct on ater de cribed so that it can and will w h tand .rot tion at hi h peripheral ve o ty, and f r the r r!! I provide .a' suitable source of motive power tor drivinezitjat the desired speed, illustratively {this may. be in the form of an leetricmotor i [Pmvided with any suitable frame or standard jor sup ort n it s ch v ss rame om risi jtw heavy and strong su porting legs 12-113 secured at th upper en s in any. sui able way to, he frame of the motor ll andprovidedat theiri'lower ends with .iootportions i4 and '15 respectively thatjha've b lt vholes L6 therein for solidly Iseuring and anchor n the structure to asuitabile base. or found tion (not shown) M An appr riate artof .this supporting .irame is conveniently 3 ,116 preferably employed to serve as a support or m n in for, ther appa at s "o vdevices] with which the .rotor I (1 is to coact as is laterjdescribed, and illustratively theioot portion 15 of the uppottins, br cketlor 1eg\.|3 has :rigidlyjses cured thereto an upstanding rm or bracket ll to which such vvdevices or apparatus are secured.

'ample 8",

The rotor In which, for purposes later mentioned, is preferably in the form of a dished disc has an outer peripheral and generally circular portion Ill from which projects a suitable number of elements It); the latter are preferably formed as an integral part of the rotor l and in the illustrative embodiment they project radially outward from the rotor portion Ill and they may, as appears from Fig. 2, lie in the same plane as that of the rotor portion III.

The rotor I0 is rotated about its axis at an R. P. M. such that the tips of the radial projections Ill travel at a velocity that exceeds the local velocity of sound in air. As is known, the velocity of sound at sea level and under normal atmospheric pressure and at 20 C. is 1,1 0 feet per second, and it varies primarily with change in temperature, that is, in general, increase in temperature of the air increases the velocity of sound, and vice versa.

The rotor [9 may be dimensioned so that'the maximum radius thereof, at the effective portions of the radial projections [0 is for exin which case the rotor I0 is driven at an R. P. M. of 16,600, giving a velocity of about 1,200 feet per second to the outer effective portions, indicated at W, of the rotor, these portions travelling in a circle indicated in broken lines by the reference character A in Fig. 1.

The electric motor I I is a convenient and suitable means for so driving the rotor 10 and because of the high speed of rotation of the rotor Ill, it is preferably made of a suitably strong material such as a steel forging suitably heat treated and dynamically balanced, and by giving it a dished form like that indicated in Fig. 2, I am enabled to provide it with a suitably heavy and strong hub portion w of relatively small radius by which it is mounted on one end of the shaft adjacent one of the end bearings 2| carried within the frame of the motor; as indicated in Fig. 2, the metal of the rotor Ill merges in decreasing thickness from the hub portion ID" to form the generally conical or dishlike side walls I0 which are internally of radii so as to take over, with ample clearance, the portion ll of the motor frame that carries the end bearing 29. The conelike portion 'Hl in'turn merges into the above-described flat peripheral portion Ill that carries the projections lll -l0 and which together lie in preferably the same plane which is preferably at right angles to the axis of the rotor. In this manner I am enabled to achieve not only good strength and rigidity in the structure of the rotor l0 but also such distribution of the metal of the rotor ID that its center of gravity coincides with the center of the bearing 21 which is one of the bearing supports for the shaft 20.

Any suitable means is employed to secure the rotor I0 to the shaft 20, preferably detachably; for example, the end of the shaft 20 and the bore in the hub Ill may be given a suitable taper and provided with conventional key-ways and a. key (not shown), whence the rotor I0 is locked. onto the shaft 20 by a clamping washer 2| and nut 22, the latter being threaded onto a suitably reduced threaded end portion of the shaft 20. Also, the rotor may thus be readily removed, as for replacement by another as lated noted.

As indicated in Fig. l, the radial projections 10 illustratively four in number, are equi-angularly spaced about the axis of the rotor and the effective end portions It) thereof, while .capable of variation in shape are, in the illustrative embodiment, substantially flat-faced along their leading edges. Thus each may be shaped to provide a flat face H! which may make an acute angle to the tangent at the point where one of its radii intersects the circle A, as indicated in Fig. 1. This inclination or angularity of face l0 is related to the direction of rotation of the rotor and also to the companion leading fiat face 10 of the arm-like radial extension Ill with which, in the illustrative embodiment, it makes an obtuse angle. The width of these edge faces is, in the illustrative embodiment, the same as the thickness of the parts Ill and I0 Where these two faces intersect, at an obtuse angle in this embodiment, is formed the effective part of the rotor that is to coact in shockwave generation, and the resultant apex or part, for convenience in further description, will be referred to by the term tip. It projects in the general direction of its rotary movement about the rotor axis.

The tip T may be given any desired appropriate conformation or shape. Thus, for example, the angles of, and the angle between, these leading edge faces Ill and W may be varied and though they are, in this embodiment, described and shown as flat, one or both may be given curvatures as may be desired. Also, where they intersect, they can intersect in a straight or curved line and according to their angularity form a tip with a relatively sharp leading edge at the line of intersection, or as in the illustrative embodiment and as indicated in Fig. 1, the region where they intersect is rounded off at relatively small radius to form a less sharp leading edge; the greater the radius of this curvature, the more blunt would be the tip T.

The direction of rotation of the rotor 10 is counterclockwise as seen in Fig. l and as indi cated thereon by the arrow, the tips T travelling in a circular path generally indicated by the broken line circle A. Suitably related to the rotor l0 and to the movement of the tips T thereof is a suitable means for effecting flow or movement of air, at a suitable velocity, in a path located so as to be intersected or traversed by the moving tip T, the air moving in a direction opposite to the direction of movement of the tips T themselves. This means may comprise a nozzle-like device generally indicated by the reference character 23; in the drawing, its intake end is at the right and its discharge end at the left. It is constructed to discharge air at suitable velocity and along a suitable path of flow. The device 23 is suitably mounted in appropriate relation to the rotor l0 and is preferably adjustably and also detachably secured in position so as to be readily replaceable. Conveniently, it is secured as by cap screws I8 to the bracket ll of the supporting frame or standard and is so positioned that its axis BB, which is also the axis of the emerging stream or jet of air, falls in the plane of rotation of the tips T and is substantially tangential to the circular path of travel A of the tips. Desirably, it is positioned as closely as possible. to the rotor [0 so long' as suitable clearance exists between the rotating tips T and the physical structure of the device 23 itself.

At its inlet end, the device 23 is supplied with air under pressure in any suitable manner and from any suitable source, such as a tank of compressed air, a blower, compressor, or the like, which is diagrammatically indicated at 25,"t0'- gether with any suitable devices, diagramaeeeeso curved mie somewhat indicated; only for rim trative purposes, in Fig; 1". iridi'a' tcl in Figs. 1 and 2; thepposea pairs of walls of the flowpassa through the eraser 23 are gym rgetrieany catedwith respect tothe axis B'B. v

Ill tfafis 'vefse 've'reeei dross-section, as shown in Fig; 3', the ow passage in the effusor 23 en-- efally'j rectafieuiai With its ranger ant vertieal 21nd falling in the plane of rotation of the tips 1. Iilthis in'ahner the ir'i hg jet of air has a substaiit'ial vr ea Hifn comparable to that of the dish'arg i'iZi of the device 23, as will later app a giesfienefigtn or' aijc 'of the (ironlai" path of Movement A of the tips T 'cai'l be friable to intersect the jet" of The diinehsions oi the flow passage at the dlschafg end ma he, illustrativly'ionthe order oil" by p As seen the vertical seamen shown in Fig 1, it 'wm be noted marine new baesege thro gh the efiu'soi- 23, in a direction froifi the right to the left, is general first convergent and then divergent, this shaping being provided by the opposed top and bottom walls; 28', "while the flow' passag n horizontal sectionand as seen i Fig'; 2 is ofthe same dimension throughout; due to the 'paraiia pIane opposed Walls 21;

The effu'sof 23 accelerates the 6' receivedfrohi pipe 24 from suhsorii personic speed. The efiiiso'i' may be bohsidred as of four p'aits. The rst part 23' adjaceht the inlet end is a converging" tube in whieh the in- 'reas'e velocity of the air is greater than the doi'respondihg decrease in its density and the air is aeceieiatea to a veloeit'y on the larder or t speed of sound at the seeona part or throat ga which is "of minimum section. The third part 23 is a aiver'g ng' time n which the increase m velo'city of the air is less than the corresponding decreasein density supersonic speed is at taih d. The fourth pait 2'3 f'enders'the e'riiitted jet substantially parallel iii new.

The source of compressed air 25 or the valves of pressure regulator 26 'are'su'ited oi se' or a jilstd and volume for which the fia-rtililai f-- ins-or 1e designed;

The euryatnies of the a trans as Shown in Fig; 1 are int i'lded to '19 01113 illusti or indicative, for it is k'rio'w'h to design effusor's to achieve any supersenie air now or jet with parallel flow or stea" y nature. For the he tails of 511611 design and "construction there f for purposes of carrying out and prac y vent ioh iffli may he made, fi -'exa-ifi ple, t0

. 6" 'faimefitsef Aei'eayiieniies or steer by mentioning potnshee 1-949 tr many; New Y he the a at that is sue the oihc'iiieiit substantially ceiit'f line of the jet or air. Iii general the fol" a substantial 'clistaiie from the d'iscliar' eiid of the armor 23; the cross 'sec t'i'oiial ar eajet of air somewhat closely approximates t t of the dischargehd 23 of the effusc 23 itsel this volumetric region in the apparatus; thus g e'ialli defined by the general dimensions? of the air stream or jet, I term; for "conven-iene; t path along whili-the air ove's'; in tnepresent: 1y assumed case at suoer'seriie velocity."

With the rotor-1 l0 rotating eeomereleelavise dii'eetioii that the tips? travel at high velocity iii the ulaf path a substantial portion or that circular path of t'r'a el- A eigterids into and through the ahov desoiihed path or high v locity air discharged from the device" 23; As i c'ated in Fig. 1, an ar'cuat portionfioni to y' the circle A may be taken as illustrative'o'r ie'pte: sehtative of the length of the 'path of movement of each rotor ti'p T within the path of movement of the air of the jet, and in a direction opposed thereto; The greater the radius to the tips T, the less is the curvature of that port-ion a: to aimthe more nearly rectilinear is the path of travel; Moreover, with substantial radius; a substantial middle-portion of the path ac to y may be said" to be, for practical purposes, closely reti-linear and quite directly opposed ifi direction to the move ment of the air of the 5et. It is accordingly throughout this middle region, of substantiatlength, that most effective straight-line relative movement, for wave generation, takes place between the tip T and the air of the jet. However; substantially similar relative velocities are eifec tive throughout the regions at the ends of thepath ar y, as at the entry end where the tip T en= ters the path of the air, and as at the exit end 1/ where the tip T emerges from the air of the jet-l As the part IOb approaches and passes point at on its way to point y, the tip '1 enters the Jet of air, piercing the latter from above and centrally of its conformation or path, and then'it is progressively more and more depressed-into the Jet of air; reaching maxiniuin penetrationthereof throughout the middle region of the path It is throughout this ihiddle reg-ion that substan tiall'y 'straight lme relative movement between up T and the air from device 23 takes place. All "0"! this, of course, takes place at high relative "velocity; and so also wlieh the tip T movesrrom the mid position in the path i y to the point 1/ where it emerges from the path of moving air.

In such manner it is possible to move or project the tip T, at high velocity, into, and opposed to, the high velocity jet of air the resultant effect is then one due to the 'ila'tive velocity arm that is the sum of the two. But the resultant wave generation is achieved at far less power consumption or input to the apparatus than would be the case were known methods employed.

For example, as heretofore practiced by the use of a high speed air jet at atmospheric pressure directed against a stationary body, the horsepower requirements to produce such an air jet increase nonlinearly or disproportionately with increase in velocity of the air of the jet and by way of illustration these figures might be noted: Approximately 22 horsepower per square inch of cross-section of air jet are required to produce a jet at sonic velocity at atmospheric pressure, but when it is desired to produce such a jet of air at three times sonic velocity (that is, Mach:3), about 560 horsepower per square inch of jet are required.

However, with the method and apparatus of my invention I am enabled, at much less power input, to attain dynamic similarity to a stationary body in a high velocity air jet by setting or adjusting the apparatus to function at any selected rotor tip velocity and any selected air jet velocity. For example, the nozzle device 23 can be constructed or designed to produce a discharge of air or an air jet whose velocity is far less than sonic velocity, for example about one-half sonic velocity, and the speed of the rotor driving motor i I selected or adjusted to give a rotor tip velocity also less than sonic velocity, for example one half, or this latter effect may be achieved by replacing the rotor III with one of such different diameter that at the given speed of the motor I l, which in such case can be a fixed speed motor, will give to the rotor tips T a velocity of about one-half sonic velocity. In this assumed illustration, much less horsepower input to the nozzle device 23 will serve to produce the desired jet velocity and less energy input into the motor I I is required to give a rotor tip velocity of onehalf sonic velocity, all in relation to power input required to produce sonic velocity, Yet the relative velocity achieved in the region or path at to y is the sum of these two velocities, in the illustration totalling sonic velocity, and the total power input is materially less than the horsepower input required for the jet device to discharge air at sonic velocity at atmopsheric pressure.

Thus a condition of Mach l can be achieved at less cost, and conditions and results comparable to values greater than Machzl can be achieved by other suitable combinations of rotor tip velocity and air jet velocity. For example, with the same nozzle device 23 of the above illustration, the resultant sonic velocity of the illustration and comparable to Mach:l can be exceeded in any desired stages or steps, as by correspondingly, that is, in stages or steps as desired, increasing the speed of the rotor to give greater than one-half sonic velocity or for a given or fixed speed of the motor, rotors of correspondingly increased diameters can be mounted on the motor shaft to give the desired increase in rotor tip velocity. To illustrate, rotor tip velocity may in this manner be achieved equal to one and one-half times sonic velocity and with the air in the discharge end of the device 23 moving at one-half sonic velocity, the action and effects in the path a: to y are thus of a velocity equal to twice sonic velocity and hence equivalent to the conditions of Mach:2.

Or, where the device 23 is an effusor designed and constructed, as above pointed out, to produce an air jet at any selected supersonic velocity, for example, twice supersonic velocity or a condition equivalent to Mach-:2, the apparatus is set, adjusted, or the rotor diameter changed, as above indicated, to give a rotor tip velocity of any desired practicable value so that the condition and results corresponding to Mach-:2 (the jet velocity) are changed and increased to be thus comparable or equal to the sum of the rotor tip velocity and the jet velocity. Thus a rotor tip velocity equal to sonic velocity (Mach:1) may be achieved but the action at the rotor tips T is that which corresponds to three times sonic velocity, comparable to Mach:3. In like man-v tion compared to the above indicated vastly disproportionate increase in power input to a Busemann type of nozzle with increase in jet velocity. Thus great savings in power input and power consumption are achieved.

Thus it will also be seen that I am enabled to achieve a wide variety of wave intensities, at the tips T as they move along the path a: to y in Fig. 1. Weak waves are produced where the sum of the tip velocity and the air stream velocity is small, the intensity and strength increasing as the sum of the velocities approaches and just passes sonic velocity whereupon, as the sum of the velocities increases further into the range of supersonic velocity, the intensity and strength of the produced waves increase still further. The relative motion between the tip T and the moving air in the jet brings about the effect of discontinuity in air flow, causing a shock wave, sometimes also called compression shock and shock front, in which the pressure and density, that is, within the Wave, are not only relatively high but also increase intensity with increase in relative velocity. Thus, the higher the relative velocity between the tip T and the moving air, the stronger is the shock wave and the more powerful are its effects.

According to the method and apparatus of my invention, the shock wave, with its apex at or closely adjacent to the tip T, comes into being when the rotor tip T enters the left-hand end, as seen in Fig. 1, of the path a: to y and the shock front or shock wave travels with the tip T and at the velocity of the tip T along the path r-y; the wave collapses or ceases as soon as the tip T moves out, as at the point 1/, of the path of the moving air emitted by the nozzle device 23. This action is repeated for as many tips T as are pro-- vided on the rotor H), and where the rotor is provided with more than one tip T, these actions at each tip T follow each other in succession, always throughout the path of travel :cy, as the tips are successively brought into and out of the air stream emitted by the device 23. The rate at which tips T are thus made successively active may, for a given rotor speed, be varied by correspondingly varying the number of tips, and for this purpose I provide a suitable number of rotors of the same diameter but with different numbers of tips '1 thereon, any one of which may be achieved.

tachedwave, these actions being yariable. in genthe nozzle deviceli. as seenin Fi s, 1. and-.2; shock w .e thus generated and; forsuch purposes ees n ed, s le tire eneration Isa wide range. 0.1-: s rength or intensity. and o cha a ter.- ist cs Q i the: s ock Wav maybe. achieved.

l-ms e ion s. rel tirelv of substantial volume a d it, or select d: portion or part thereof, and; e i ns, ad acent. ther tcmav be utilized; for stud and investi tion. or orsubie t on of: subie bodie r a ticles.- Eor example, spec men or; var ous materialsorccmncs tions or ma erials, cu es spe im ns of various sha es. structures. o thelikemar by any suitable m aps e positioned in. this. region. or; trea ment Zane, or moved or passed t ou h the. treat.m r t. tone or p rposes oi mechanicaltestin or determination. of: characteristics under subjection to shock waves or shock fronts, and in this connection-itwi-ll; also. be noted that accordingto my me hod and: apparatus, any one of a widerange of shock wave characteristics and. properties may-be selectively.-v producedg. Thus also, continued research, study and investigation ofshock waves and. their effects. are facilitated.

It will thus. be. seen that there. have. been pro,-

vided an apparatus and method in winch the. severa-l Objects of: my invention are successfully I- am enabled to reduce. materially power consumption and hence. cost of operation is also lessened materially, and in part also because of relatively low power requirements, first cost. of the, apparatus is. of a materially. lower order of magnitude. Moreover, the, metho and allparatus provide, in a simple, practical and economical manner, a wide, range of flexibility or variability of; execution or operation, and thus a substantial range of practi al requ rem nts a for the. treatment. or testing of v ri us subject bodies, articles, devices or the like, may be easily and readily met, While, for purposes .Of research and investigation, the facility and relatively low cost of achieving the production of shock waves or shock fronts of a wide range of characteristics are. of great advantage.

Inthis latter connection, it might be noted that,

as above indicated, the shape or configuration of r the tips T may be varied; a sharp leading edge generally results in the production of an attached wave and a blunt leading edge on the tip '1, such as a cylindrical surface of relatively substantial radius, results, in general, in producing an u nateral according to the range of relative y em ey d also, ityvill be noted that the rotor and its ivc s u d surr iv The near H while preferably a high speed motor, may be of any suitable type and where change in R. P. M.

is desired, it may be of any appropriate design to change the number of poles and thus to change the R. P. M. Where rotors IQ of difierent diameters are interchangeably provided, this may be done with or without change in speed of the motor I l and thus flexibility of control and of op eration may be extended, or may still be achieved driving means are capable of e bodimeri t inrela- 1.0 f -ths mciqr I?! is a, ites steed: mete rotor diameters, h

t. l i h We l Q1 3': retort". s. so s ap d nd cup,- ioi to ts wei h and: the s a t e in 2. ore, descr bed. th center c rav y- Qt ti coincides t he center of the bearing 29, thereby lessening ten dency, to stress the shaft 2!] by forces tending. to bend it s can emused: by the un mmetr a o d on h roto a its. s. coas w t wi ai emitted v-the nozzle. dev e 3- As, man ossible. mbo men s may be made t ec an cal feat res fthe abov tion; and as the art he e d s bed mi ht be varied in vario s pa ts, al w outepart from the cope of; the invention, it i to e und r.- stood that all matter. hereinabove set forth or shown in the a c m an n d awi s is. tov be interpreted as illustrative and not in a limiting sense.

I claim:

1. An apparatus for generating shockwaves comprising an airedischarge nozzle having an inlet for receiving air and having an outlet for discharging air. in' a stream of substantial cross.- section, a rotor having a projecting part thereon radially spaced from its axistand movablegupon rotation or the rotor, in a circular. path, means mounting said nozzle adjacent said rotor'and with its axis of air discharge in .line' with the plane of said circular. path and with a substantial arcuate portion or said path intersecting 'Ithe cros -section of the discharged airst'ream, means for supplying said nozzle at'its inlet end with air under pressure and "therebyfto'coact with said nozzle, to effect high'velocity of airzdischarge therefrom, and-means for driving said rotor. at a speed to give said projecting part; thereon rela- .tively high velocityand in a 'direction'to move through said arcuate portion of its circular; path in a direction opposed to the direction of movement or air in said stream'. i

2. An apparatus as claimed in claim 1 having a disconnectable driving connection "between said rotor and said driving'means therefor, whereby the rotor may; be replaced by another in which the radius of its projecting part is different, and means adjustably supporting said air discharge nozzle to relocate it in relation to the differently-diametered replacement rotor.

. 3. An apparatus as claimed in claim 1 in which said rotor driving means comprises a shaft and bearing means therefor adjacent one end of the shaft, together with means for supporting said rotor on the last-mentioned end of said shaft and near said bearing, said rotor being substantially dished and having its center of gravity substantially coincident with the center of said bearing.

4. An apparatus as claimed in claim 1 in which said rotor has at least one more projecting part thereon, said projecting parts being angularly spaced from one another and all of them moving 11 substantially in said circular path, whereby said projecting parts are successively brought into coaction with said moving air stream.

5. An apparatus as claimed in claim 1 in which said nozzle has structural characteristics comprising surfaces extending from said inlet to said outlet and forming a flow passage therebetween and coacting, upon receiving air at said outlet at the pressure of said supplying means, to discharge air therefrom at less than the local velocity of sound in air.

6. An apparatus as claimed in claim 1 in which said nozzle has a flow passage between said inlet and said outlet bounded by surfaces that include opposed curved surfaces coacting, upon receiving air at said inlet at the pressure of said supplying means, to accelerate the velocity of the air to a value, at the discharge end, at least as great as sonic velocity.

'7. An apparatus as claimed in claim 1 in which said rotor driving means has driving connections with said rotor to drive it at an R. P. M. which, in relation to the radius of said circular path, effects movement of said rotor projecting part at a linear velocity equal to or greater than the local velocity of sound in air.

8. An apparatus for applying shock waves to a subject body or bodies, said apparatus comprising a treatment zone having at one end thereof means for flowing a stream of air across the zone and at high velocity, and means for creating discontinuity in the flow of said air stream and comprising a solid part having means mounting it for rotary movement about an axis and in a circular path of movement of which a substantial arcuate portion extends into said air stream and in a general direction lengthwise thereof, and means for driving said mounting means in a direction to move said discontinuitycreating means at substantial velocity and in a direction,along said arcuate portion of said circular path, opposed to the direction of movement of the air in said stream.

9. An apparatus as claimed in claim 8 in which said means for flowing air comprises nozzle means having a flow passage with walls thereof configured to accelerate the velocity of the air moving therein and discharge it therefrom at a velocity equal to or greater than the local velocity of sound in air.

10. An apparatus as claimed in claim 8 in which said driving means drives said mounting means at an R. P. M. which, in relation to the radial distance of said solid part from said axis, effects movement in said circular path at a velocity equal to or greater than sonic velocity.

11. The steps in a method of generating shock Waves which comprise flowing air at a velocity a along a path of substantial cross-section and causing a shock-wave-producing discontinuity in said flowing air by moving a body at velocity b along said path and in a direction opposite to that of said flowing air, where the sum of a. and b is in the range from just below sonic velocity to and including supersonic velocity.

12. The steps in a method of applying shock waves to a subject body or bodies which comprise generating shock waves in a treatment zone by moving, at high velocity, a solid body within and opposed to a stream of air flowing at high velocity, and thereby generating a shock wave that travels along the path of said solid body, and bringing the subject body or bodies into the path of travel of said travelling shock wave.

13. An apparatus for generating shock waves comprising means for producing and directing an air jet of velocity a, a solid body of lesser cross section than the transverse cross section of the air jet, and means for moving said body at a velocity b within the air jet and in directions opposed to the direction of flow of the air jet and substantially at right angles to the said transverse cross section of the air jet, the sum of velocities a and b being in the range from just below sonic velocity to and including supersonic velocity.

14. An apparatus for applying shock waves to a subject body or bodies, said apparatus comprising a treatment zone having means for producing a stream of air flowing at high velocity and for directing the high velocity stream along said treatment zone, a solid body, and means for moving said solid body at high velocity within said high velocity stream and in direction opposite to the direction of flow of said stream of air and substantially at right angles to the transverse cross section of the air stream, the sum of the velocity of the stream of air and the velocity of said solid body exceeding sonic velocity, thereby generating a shock wave that travels along the path of high velocity movement of said solid body.

FRANKLIN S. SMITH.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 668,484 Bok Feb. 19, 1901 852,646 Blake May 7, 951,346 Stevens Mar. 8, 1910 1,786,264 Reed Dec. 23, 1930 2,163,650 Weaver June 27, 1939 2,248,459 Kieskalt July 8, 1941 2,570,081 Szczeniowski Oct. 2, 1951 

